Devices and methods herein generally relate to multifunction machines having document scanners such as printers, copiers, and/or multifunction devices and, more particularly, to platens using electrochromic windows for calibration of the scanner.
Generally, a document scanner converts images and/or text on a hardcopy of a document into electronic form. The document scanning process involves placing the document on a top surface of a transparent platen (e.g., a flat glass plate). A scanner carriage is then moved past the document along the bottom surface of the platen. The scanner carriage includes a light source that illuminates the document and, particularly, the images and/or text thereon. The carriage also includes an image sensor, which incorporates photosensitive devices (e.g., photodiodes or other photosensitive devices) that measure the intensity of light reflected from given areas of the document. The sensor data is then translated from analog to digital, thereby defining the picture elements (i.e., pixels) of the document being scanned. Combined, these pixels represent the document in electronic form.
Another example of a document scanning process involves a constant velocity transport (CVT) scanning system in which the document moves and the scanner carriage is stationary. In the CVT scanning system, a single stationary scanning system is utilized to scan the entire document while the document is moved past the scanning system. The CVT scanning system, conventionally, includes an image sensor, such as Contact Image Sensors (CIS) and CCD array systems, and a light source. As in the platen scanning system, the image sensor receives light reflected from the document and converts the light into electrical signals representing the intensity of the received light. The electrical signals are then passed on to an electronic subsystem which performs the necessary image processing operation so as to prepare the image data either for display on a display devices such as a CRT/LCD, for storage by a storage device such as a CD-ROM/Flash/Hard Drive etc., or for recording or printing on a medium, such as a document, in a similar manner as described above.
In current implementations of devices, such as printers, copiers, and fax machines, the scanner white reference is calibrated by moving the scanner head relative to a white calibration strip, or conversely, moving the calibration area relative to the scanning point. In either case, the scanning is performed through a clear glass area.